Conical projection
Topic: Map Projections · NCERT: Class 11, Ch 4 "Map Projections"
Meaning
A conical projection is made by placing a paper cone over the globe so that it touches the globe along one parallel. The graticule is projected onto the cone, and the cone is then cut open and laid flat. Parallels become arcs, and meridians become straight lines spreading out from the pole. The parallel where the cone touches is called the standard parallel, and scale is true along it. Distortion grows with distance from that parallel, so this projection suits mid-latitude areas that are narrow north-south but long east-west.
Example
The simple conical projection with one standard parallel is used to map the Trans-Siberian Railway across Russia and the Canadian Pacific Railway. In India, it is used for the Narmada valley, which runs east-west across central India.
Don't confuse with
- Polyconic projection: here every parallel is drawn as an arc of its own cone, not of one single cone. The Survey of India used it for its older topographical sheets.
Related concepts
- Developable surface
- Non-developable surface
- Cylindrical projection
- Zenithal projection
- Normal projection
- Oblique projection
- Polar projection